Program-selecting circuits



` nasal-53 l J. F. TooMEY PROGRAM SELECTING CIRCUITS April 17, 192s;

Filed Dec.. l0, 1925 y -EqL/amwww ma l l I l 1 l t ATTORNEY latented Apr. .17; 1928.

UNITED STATES.

1,666,153 PATENT OFFICE.'

, JonN r. Toom, .or NEW Yonx, N. y., lalssrcmon. 'ro AMERICAN TELEPHONE AND l .fm1-mwa comPaNY, a oonPonArroN o F NEW You.

PBOGBAM-SELECTING CIBCU ITS.

AApplication led liecember 10, 1923. Serial No. 679,736.

This invent-ion relates to transmission systems for transmitting 'programs over wires and more particularly to arrangements for the selection of programs for such systems.

Where wire lines, such as ordinary telephone lines, for example, are used for the transmission ofprograms, such as news, lectures, concerts andl thelike, it is desirable thatv some arrangement be providedwhereby.l the subscriber may automatically select the particular program which he desires to hear. In accordance with the present invention .it is proposedv to accomplish this result by providinv relay arrangements at the cenl5tra1 oiice w ich may subscriber at the subscribers station to connect the terminals of the subscribers line to the terminals of any one of a number of trunks, each leading to a diierent program. By theuse of selective means of. the type referred to itv becomes immaterial whether the program be transmitted at yoice vfrequencies or carrier fre uencies and it' also becomes immaterial w ether several pro- A grams be transmitted at the same frequency or whether different carrier frequencies are used for different programs. VThe selecting varrangement maybe used eitherin conncction with a system in which special transmission,- lines .are provided for subscribers to the broadcasting system or it -niay beused in a system in which the program transmitlting apparatus is superpose-fl upon ordinary` telephone lines. v The-invention will now'be more fully un# derstood from the following description when read in connection with the accompanying drawing, Figure 1 ot which'illustrates the selective arrangement as applied- '40 tofa system employing special transmission circuits for theprograms and Fig. 2 of l which shows a selective arrangement applied to a program system employing carrier frequencyprograms superposed upon ordinary telephone lines.

Referring to Fig.'1, L designates a special transmission circuit leading from a program station to a subscribers station. At the subscribers station a loud speaker .LS is providedwhich may be connected to the line hy the operation of the key K. At the broadcasting .point a lplurality of trunks Ta, Tb and Tc lead to'dierent program sources which will be hereinafter referred tov for convenience as lprograms A, B, and C.

be controlled by the.'

' a resistancel the line L over the back contacts of the re- -lays 1 and 2. When relay 2 is operated,

program B is connected to the line L over the front contacts of said relay and when rela 1 is operated program C is connected to t ie' line L over the front-contacts of said relay and the back contacts of the relay 2. These relays are controlled by a relay 3 and by a marginal relay 4, which are associated with the line L through a simplex connection to the midpoints. of an impedance 5 bridged across the line at the central station. At the subscribers station asimilar bridged impedance 6 is provided and from the midpoint of this impedance a connection extends to'a selecting switch S.

Further details of the' ap aratus will be clear from a description o the operation'v which is as follows: Assuming that the subscriberdesires to receive. a. program'transmitted over thel trunk Tmthe subscriber closes the key` K, thereby vbridging'the loud speaker LS across the -line at contact 7 and at contact Bclosing the connection from the impedance 6 to the selecting switch S. The' subscriber4 then moves the switch-S until 'it rests upon contact B, whereupon a circuit is completed from ground through a resistance 9, over the switch S, @contact 8 `and thence in parallel throughthe two'halves of the impedance 6 over two sides of the' line, in parallel and thence through the two halves of the impedance 5` to' the midpoint thereof, v from which point the vcircuit extends through the winding of the'relay 3 and througl .t ie winding of marginal relay 4 to'battery.' Relay 4, beingv marginal,- is not energized in series with the resistance 9 but the relay 3 isenergized and upon attractngits armature completes a circuit from ground, 'over the back contact of relay 4, upper front con- 100 tact of relay 3 andl through the winding'of relay 2 to battery. l

It will be noted that each of the trunks leading to'programs is terminated in a suitable resistance' (equivalent to that of a trans- 105 mission line) when the trunk is not actually connected to a' transmission line. For 'example, the trunk Tb has a resistance'Rlj bridged across its terminal, the trunk Tc has R., bridged across its terminal, 11o

- main deenergized. Consequently, the circuit while in the case of the trunk Tb a lresistance Rb is arranged to be bridged across the terminals when the trunk Tal (which is normally connected to the line L), is disconnected 'from the line. The relay 2, upon being operated, disconnects the resistance Rb from thetrunk Tb at its lower contact and at its remaining contacts connects the line L to the trunk Tb. At the same timek relay 3 at its lower contact bridges the resistance Rb across the trunk 'la in order to take -the place of the resistance of the line L, which, it will be noted, was disconnected from the trunk Ta upon the operation ofthe rela 2. Y

It the subscriber should desire to select the program C he will move the switch S to the contact C, thereby completing a circuit similar to that already traced or the relays 3 and 4, except that 1n this instance the-resistance 9 is omitted. The current now flowing through the windings of the relays 3 and 4 is sullicient to energize both relays. Accordingly, relay 4 at its upper contact opens the circuit previouslyy traced for the relay. 2 over the upper front contact of the relay 3 and closes a circuit for the relay 1 from ound, overthe upper front contact of reay 4, winding of relay 1, to battery. Relay 2 is now released and at its lower contact again connectsthe resistancel Rb across the trunk Tb. -At its remaining hack contacts the relay 2 connects the line L to the armatures of the relay 1. Relay 1 at its lower contact opens a. circuit of the resistance Rb and at its remaining contacts disconnects the tru'nlr- Ta from the line L and connects said line to the' trunk Tc. The resistance Rb is connected to the terminals of the trunk Tb over the lower front contact of the relay 3.

-If the subscriber should desire to receive the 'program A, he moves the switch S to contact A. This opens the simplexV circuit previously described for the windings of the relays 3 and 4 so that both relays will rewill he inv the condition shown in the drawing with the 'line L connected to the trunk' T. over the back contacts 'of relaysf2 and 1 in series.

It will also be noted that theV resistance Rb is disconnected 'from the trunk 'Ia at the lower contact oi relay 3 and that resistances Rb 'and Re are bridged across the trunks Tb and Tvc respectively at the lower` contacts of relays 2 and 1. i

Fig. 2l illustrates a relay program selecting arrangement applied to a wire program system in .which the programs are trans- 'l -mitted 'at carrier frequencies and vsuperposed upon an ordinary subscribers telephone line. ln this case, the line L is anv ordinary subf scribers `line terminating in the'usual suh station set C at one end and terminating at 'a central oilce in the multiplejacks ,l and J. 'A ground connection is established to inocente the'ti'p side of the line L over the back con tact of the cut-olf relay C0, said ground connection including the winding of the line relay LR and one Winding of a differential relay DR. A battery connection is established lto the ring side of the line over the back contact of the cutod relayCO, said connection including a winding of a marginal relay MR and one Winding of the differential relay DR. y

'Thethree relays DR, LR and MR jointly control the switching of the line L to any one of three trunksv Tb, Tb and Tb, leading to three programs A, B and C. This control is exercised through the relays l and 2. The trunk Ta is normally connected to the line L over the contacts of the relays l and 2 and through conductors 11, which include a highpass filter HP. vlflhen the relayl is actuated the line is connected through the conductors 11 to the trunk Tc. -l/Vhen the relay 2 is actuated, however, the lineL is connected through the conductors 11 to the trunk Tb.

At the subscribers station the switching relays are controlled to select ,the desired trunk by means of. non-lockingheys A, B and C, which are associated with conductors '36 bridged across the line L at the subscribers station. The conductors 36 are connected through a high `pass filter HP and suitahledetecting and amplifying apparatus to theloud speaker LS. y

The amplifying and detecting apparatus already referred to may comprise a detector tube DD, anarnplitierdetector 'AD, a rectifier tube RR and an amplifier tube AA, The circuits of the detector tube may be of the ordinary type including, or example, a grid condenser 37 and grid leak 38 in the input circuit. l the tube DD be a tube ot" the sev-called peanut type, platecurrent may be furnished b a source'consisting of dry batteries 39 an ila'ment current may be supplied by a source consisting of dry batte-ries` 40. ThetubeAD may also be a peanut tube arranged to act as an amplilier. The fila,- ment circuit of this. tube may he -energizei'l by the battery 40, the ilament being connected in series with the ilament of the tube DD.. The plate current `for the tube AD may be furnished. by a source COHSS-ilgf i dry batteries. 39.A A

i The l'output'circuit of the amplifier ADA is connected hy means of a transformer 41 with the input or grid circuit of the amplifier AA. whose output circuit is in turn connected through transformer 42 with the loud speaker LS. SincetheampliierAAisusuallya power f tube and therefore requires large currents for its operation, it isfdesirable to obtai-nthese currents from the local power mains.- ln the -1 ser lll)

lib

case illustrated it is assumed that alternating 'current is supplied 'tothe power mains 43 hy closing a switch 44; the alternating currentfor the power mains may 'he imgenius-.-

i pressedfupoii ofi' af'transfv former.' The .transformerhas threesecond'- aries: `,By --ineans'j of secondary 146 the lyolt ageofjthejpower source is s ter'iped downto ment Cjo'fthe vam'p'lltier of .the tube j The? .plate current; for' the amplifier is; sup.-

` plied through the rectifier RRQ-f The:

ondary winding 48of the transformerhl- 'the power mains to a proper-voltagefor enready referred to steps down the lvoltage of ergizing the filament .of the rectifier` RR.

The current to be rectified is impressedupon amplifier-AA extends fromthe midpoint of the secondary winding 46 (which is connected vwith the filament of the tubaAA.)

lthrough a resistance 49,- through the secondary .windingr47, plate of the rectifier BR,

Vthence *through the vacuum of. thetube-to the-filament of the rectifier RR, and from tle filament of. the rectifierRR'the 'circuit extendsto the winding oftherela. 50 .and

, :through t-lieprimary4 winding oft e trans- *former 42 Ito theplhatf'e of the amplitieraAA.`

It 'will .thusbc seen that the rectifier, .RR is included in the plate circuit of the 4tube f andur'ectiiies ,the current impressed upon saidtubethrough the secondary winding 47.

This current when flowing energizes the re? lay to Aclose the lament 'circuitof the.'

l fdetector tube- DD. Consequentl by merely Vclosing the switch 44 the recti er and amplier circuits are suppliedwith current,

` thereby being rendered operativa/andthe current owing in the `plate of the power l -amplifier circuit 'operates the relay 50 to set lthe detector DD and amplifier AD in operation. Opening the' swltch 44 disconnects .j the current supply from the rectifier and the amplifier and the cessation of 'current flow in the plate ofthe amplifier causes the relay Y' 50 to disable the'detector DD and lthe am- Furtherfdetails of the apparatus will be'4 cut-off relay winding of the differential relay DR and pufier AD.

clear from the description of the operation which'is as follows: Assuming that the subscriber wishes to hear theprogram B, he first closes the switch 44, thereby connecting the power mains to the amplifying appara-l tus and rendering thel amphfymg and detect- -ing apparatus operative-in the manner already described The non-locking key' B is then momentarily operated. This closes a circuit from ground, through resistances and 61 'in series, over the ring side of the line L` over the lower back contact of the CO, through the right-hand through the Winding' of the marginal relay MR to battery. The relay lMR is marginal and notenergized'- series with the 1'e sistances 60, andxl, ;.'1-l1e. differential relay ing 'of marifinal relay 1, @upper winding ,ofy

1DR,.h0wever5.is'eilergizedand closes a cir-.f cuit from battery, throughV the upper wind'- marginal ire ay-2, lover theffront-contact of the'V relay `Dlt-fand through the highresi'stvance windingofgthe'relay 62`to round. Re- L lays 2 `and 62 are energized byt 1e closing of` thisA circuit but relay 1,-wliich is a marginal relay, will not operate inseries' with the ,high

resistance winding Qt-hejrelay 62 andthe upper'windingfof thefrelayr2.

theftrunk Relay v2. disconnect T, ,leading 'to the program 'A'fro'm theconductors 11 aud colyinccts 4thelco'nductors 11 to the trunk closes a locking circuit from batter-through 'its lowerwindingand over its lower front contact,over the lower back contact of relay 1 and over the back contact of relay 62 to ground. Thiscrcuit is, not closed, however,

unt-ilthe subscriber releases the key B, therevby, decnergizingl the. differential relay DR; and; opening the circuit previously traced `fo1 `the`. relay 62 and the relay 2.- As the relayv 62 is quicker to release than the re layf 2,fthis locking circuit is established be- Afore-the v,initial energizingcircuit of the' relay2 is opened. -It .will be clear, therefore, that-"(mcejthe relay '2 has' been actuated to connect the line over conductors 11 -to trunk Tb' it will remain :thus connected until some other key is`actuated. The operation of the relay- 62 .whenf'the 'keyB is actuated, of course,'holds open the locking counectionand therefore releases 'the locking circuit of the relay 1, in lcase said vvrelay had been previously energizedand locked up inamanner to be described later.`

. lIf, now,'thc subscriber desires-to hearthe program C, he will .momentarily lactuate the non-locking key C.; -This completes'l a M .circuit from ground, over the-' keyll'C, Aover the ring conductor of the. line L, over the righthand winding of differential relay-DR and through the winding` ofvr'nargina'lgrelay- MR to battery. As rsistances (S0-and '61jv are' not .included -in this circuit'bothidiffereutral relay; DR and marginal relay MR Aare energized. Marginaly relay MR.com-' lpletes a clrcuit. .from ground, over its front contact, over the 'frontcontact or' 'differenf tial relay DR, through the upperA wind- 'ings of relays 2 and 1, tobattery. "Both relays 2 and 1 are operated as the circuit just" traced did net include the high resistance winding of relay 62.l Relay 1V disconnects the conductors 11 from the conductors leadingto the contactso'f thejrelay- 2 and connects comn."

ductors 1 1 to'the 'tivunli TM- QTlle'fact that the relayf2is energized fatthis -tin 1e'`is withl out effect. to connect the -trunlrTgto'tlle line as the connection ofthe trunkiTgInust vex;

i101 l lower back contactpof the cut-off relay CO. I

tendover the mormalback contacts of the relay 1, which is operative. Relay 1 at its lower front contact establishes a locking circuit through its lower winding, over `its lower front Contact and over the back Contacty yof relay 62 to ground. This locking circuit 1s established immediately WithoutI awaiting the release of the key C as the relay 62 at this time is not operative. The lower contact of the relay 1, on the other hand, opens the' locking connection through the lower winding of the relay 2 so that as soon as the key C is restored relay 2 is deenergized and only the relay 1 remain lockedup to maintain the connection between the trunk 'lc and the line L.

It, under lthe conditions above described, the subscriber should desire to shift his connection to the program A, he will momentarily actuate the non-locking key A. This completes a circuit Y from battery, through the winding of the marginal relay MR, through the right-hand Winding ofthe dif-. yferential relay DR, over the lower back contact of the cut-olil relay CO, over the ring conductor of the line L, through the high resistance (S1, over the contact of keyvA., over the tip .conductor-of the line L, over the vupper back contact of the cut-ott rela-y CO, through the lett-hand Winding of the diierential relay DR and through the line relay LR. lhe differential relay DR will not be operated over this circuit as current is flowing through both of its windings. The marginal relay MR will also not be operated for the reason that the current HowingV through the high resistance 61 is not sufficientto energize its winding. Relay LR will be actuated, however, and will com plete a circuit from battery, through the line lamp over the front contact ot the line relay LR and through the high resistance winding of relay 62 to ground.

The resistance ot the winding or' relay G2 is sutliciently great to prevent actuation oi. the lamp 35 so the line lamp does not glow. rlihe ,rclayh62 is energized, however, and opens the locking circuit for the relay 1,

i restoring` the contacts of said relayto nortitl mal so that the line la is connected with the trunk 'la over the conductors 1l and over the bacle contacts otn relays 1 and 2. The connection to the truuk T., is, ot course, opened by means ot the relay l at the same time. Had the connection previously established been over the contacts of the relay 2 to the trunk Tb the relay 62 would open the locking circuit ot the relay 2- and restore this relay to normaLthereby opening the connection to the trunk 'lband connecting the trunk "lla tothe line L. As soon as the 'key A. is restored the relay LR' is released and the circuit ot the relay 62 is opened. This does rot, however, produce any change in the seti ing ot the' circuit. lt

'Locarno neither relay 1 nor relay 2 has been previously actuated to connect the line to a program other than the program A it would,

or' course, be unnecessary toactuate the key lf, while the subscriber is receiving any one ot' the programs above referredto, a `telephone call should comey 1n for the subscriber the operator will insert a plug in the multiple jack J ,'thereby operating the cut` oil' relay. lhe cut-ott' relay disconnects the.

vwindings of the differentialy relay DR and the line 'relay LR and marginal relay MR from the line L but in so-doing it does not canse any circuit change Aso'far as the connection to any given grogram is'concerned for the reason thatthese relays are'only Y momentarily operated over the lline by the non-locking key at the subscriber-s station and their continued energization is not necessary to maintain the connection Aot thel line to a given program. rlhe subscriber may then be rung in the usual manner and upon removi'ng'hisreceiver tromthe switchhook may carry on a conversation with the calling` subscriber. llhis may be'done without anyinterterence with the program` transmitted as the high pass filter HP? prevents-the ordi nary voice frequencies from entering the re-v ceiving program circuit. The program be ing broadcasted atA carrier frequencies will be inaudible and will therefore not interfere with the conversation. lt will also be understood that several programs hereinbefore referred to, may be transmitted either at the same carrier frequency or a diii'erent carrier frequency maybe used tor each program. in either case. the high pass tilters segregate the program from the telephonie range and the selectingrelays connect one program only to the line at a time. v

ln case the subscriber should desire to make a telephone call while a program is being received, he removes his receiver from the switchhooh.,y thereby completinga low resistance circuit from battery, through the marginal relay MR. through the right-hand winding oit the ditlerential relay Dit, over the lower back. contact of the out-ott relay CG, over the ring conductor of the line L, over the switchhook. backover the tip conductor ot' the line L, over the upper back contact ot the cut-ott' relay CG, through the left-hand winding ot the dierential relay Dit and through the winding' ot the line re lav Lit. The 'diiiercntial relay Dit will not be actuated it the current tiows through both tit-these windings.. @wing to the low resistico lin

ree

`mamma ,lance path established', however, both mrginal relay MR and the line relay LR will be actuated. A circuit will therefore be coinpleted from ground, over the front contact of the relay MR, over the front contact of relay LR, through the line lamp 35, causing the-line lamp to glow. No circuit will .be

completed for relays 1 and 2 as the circuit ofthese relays will be opened at the contact of the differential relay DR, which l1s not energized. No circuit is'established for the A lamp 35, will insert the plug lof her cord in the answering jack J, thereby energizing the cut-ott' relay.` The cut-otf relay d1sconnects the diti'erential relay DR, the line relay LR andthe marginal relay MR from the line, as previously described. This elaces the line lamp butter reasons already stated does not produceany change in the connection previously established. The con- 'versationwill now take place as in the manner already' described.V

Whenever the subscriber desires to cease receiving a given program all that is necessary is to open the switch 44, which disables the amplifying and detecting apparatus. .It is unnecessary -to manipulate any of the keys A, B and C. It will'be-understood, of course, that the various resistance values,l etc., assigned to certain of the elements upon the drawing are for purposes of illustrations merely and these particular values'are not essential to the proper operation ofthe eircuits.

It willbe obvious thatthe general principles herein disclosed may be embodied` in many other organizations widely different from those illustrated withoutV departing from the spirit'of the invention as definedinthe appended claims. v

What is claimed is:

1. In a rogram transmission system, a line extending from a. :centralotiice toa program subscribers station, a, plurality of trunks at said central otiice upon which pro' `grains may be impressed, relay operated switching means for establishing connections between any one of said trunks and said line to the exclusion of the others, and means at the'subscribers statieii to transmit over the ,line selective currents to selectively actuate said switching means to select the desired trunk, said current so transmitted program being maintained uninterru ted both during the'operation of trunk se ection and during thecontinuance of the established program connection. l c,

2; In aeprogram transmission system, a line extending from a centraloice to a pro gram subscribers station, a plurality l of trunks at said central otiice upon which programs may be impressed, selectively operatn ed relay means for establishing connections between any one of said trunks andsaid line to'theexclu'sion of the others, and means at the subscribers station to transmit over the line selective currents to selectivelyl aetuate said relay means to select'the desired A programtrunksaid current so transmitted being maintained'uninterrupted both during the operation of trunk selection and during the continuance of the established programconnection. y

3. In a program transmission system, a line extending from a central oflice to a -program subscriber-s station,'a plurality of trunks at said central otiice upon which programs may be impressed at carrier frequencies, relay operated switching means for establishing connections between any one of said trunks and said line to the exclusion of the others, and means at tlie'subscribers 'station to transmit over the line selective currents to selectively actuate said switching means `to select the desired program trunk, said' current so transmitted 4heilig maintained uninterruptedboth during the operation of trunk selection and during the continuance ot' the established program connection. y 4. Inra. program transmission system, a line' extending from a central ofiice to aprogram subscribers station, a plurality of trunks at said central office upon which programs maybe impressed at carrier frequencies, selectively operated relay means forestablishingconnections between any one of said trunks and said line to the exclusion of the others, and means at the subscribers station to transmit over theline"slective currents to selectively. actuate said relay means to select the desired program trunk,

said current so transmitted being maintained uninterrupted both during the operation of trunk selection and during the continuance ofthe established program connection.

5.l In a program transmission system, a '.subscribers telephone line terminating in4 a subscribers telephone apparatus at they sub-l scribei"s station. switching means at the lcen-` tral office whereby 'connections maybe established between said subscribers line and another subseribers line, a plurality lof trunks at the central otiice upon which-pro# grains may be impressed, relay operated switching means independent of, said first mentioned switching means at the central oiice forestablishino' connections between any one of said trunks and said line to the exclusion of the others, and means at the while the receiver is on the switch hook. v

6. In a program transmission system, a

-to the exclusion` of the others, and means at the subscribers station for controlling said relay operated switching means wlnle the receiver is on the switch hook.

7. ln a program transmission system, a subscribers telephone line terminating in a subscribers telephone apparatus at the subscrihers station, switchingy means at the central ofiice whereby connections may be established between said subscribers line and anothersubscribers line, a plurality of trunks at the central oiiice upon which programs may be impressed, relay operated switchingr means independent of said first mentioned switching means for establishingr connections between any one of said trunks and said line to the exclusion of the others, and means at the subscribers station for selectively actuating said relay means While the receiver is on the switch hook.

8. In -a program transmission system, an ordinary `telephone subscribers line termimating` ina subscribers telephone apparatus at the subscribers station, switching means at the' central oiiice for establishing connecmemes tiens 'between said line and other lines so that telephone conversations may take place at ordinary telephonie frequencies, a pluralit of trunks at the central oihce upon which di ferent programs may be impressed-at carrier frequencies, relay operated switching means independent of sai-d first mentioned switching means for establishing connections between any one of said trunks `and said line to the exclusion of the `others,`and means at the subscriber-s station for controlling said i relay voperated switching means while t-he receiver is on the switch hook.

9. ln a program transmission system, an

ordinary telephone subscribers line terminating in a subscribers telephone apparatus at the subscriber-s station, switching means at the central office for establishingconnec-A tions between said line and other lines so that telephone conversations may take place at ordinary telephoniel frequencies, a plurality ofytrunls at the central ofiice upon which diierent programs maybe impressed at carrier frequencies, selectively operated relay means independent of said firstmentioned switching means for establishing connections between any one of said trunks and said line to the exclusion of the others, and meansA at the subscribers station-or-selectively actuating;r said relay means while the Y receiver is 'on the switch hook.

'In testimony whereof l have signed myv name to this specication this 7th day of December 1923. v

Jorian. Toor/mr. 

